(p,ρ,T,x) and viscosity measurements of {x1n-heptane + (1 − x1)n-octane} mixtures at high temperatures and high pressures

Density and viscosity measurements are reported for {x1n-heptane + (1 − x1)n-octane} mixtures at x1 = (0.2808, 0.5427, 0.7906). The measurements of density and viscosity were made with a constant-volume piezometer immersed in a precision liquid thermostat and a capillary flow technique, respectively. Measurements were made at pressures up to 10 MPa. The range of temperature was (293 to 557) K for the density measurements and (298 to 473) K for the viscosity measurements. The total uncertainty of density, viscosity, pressure, temperature, and composition measurements was estimated to be less than 0.06%, 1.6%, 0.05%, 15 mK, and 0.02%, respectively. The effect of temperature, pressure, and concentration on density and viscosity of the binary {x1n-heptane + (1 − x1)n  -octane} mixtures was studied. The measured values of density and viscosity for the pure components and mixtures were compared with those generated by reference equations and prediction techniques for the mixtures. The excess molar volumes VmE and the viscosity deviations Δη were derived using the measured values of density and viscosity for the mixtures and pure components. The viscosity data have been interpreted in terms of the Grunberg–Nissan equation for binary mixtures. The temperature dependence of the Grunberg–Nissan constant was studied using the present viscosity data. The molar excess Gibbs energy of activation for flow ΔEa was also calculated from our experimental viscosity data for the (n-heptane + n-octane) mixtures.